The present invention relates to a method for banding groups of sheets, in particular bank notes.
The present invention is advantageously applied on machines which arrange bank notes into groups then transfer them to a banding machine which applies at least one band to each group of bank notes, thus securing them in position.
As is known, the institutes which issue bank notes, also known as the central banks, and commercial banks have to handle large quantities of paper money every day. For this purpose, the bank notes are first divided into groups, then placed in bags or boxes for transportation.
To hold such groups together and transport them without the risk of the notes separating and also in order to prevent tampering, bands are applied to them, securing them in position and preventing theft from them.
For this purpose, bank notes are loaded into the above-mentioned machines in succession and, once checked and divided according to their value and/or type, are sent on to the various group formation channel outfeeds.
A stack of individual bank notes forms at each of these outfeeds and, when a given number is reached, defining one of the above-mentioned groups, they are picked up and transferred to a banding station, where a band is applied to each group.
For the above reasons, banding must be rapid, precise and must provide a strong, high quality finished product. Particularly in the case of the central banks, freshly printed bank notes must be handled with extreme care, to prevent accidental damage which could compromise their issue.
Bands are applied to the groups of bank notes by known machines, comprising a unit which projects and feeds a continuous web, unwound from a reel, and a circular channel along which the web is fed, pushed by the projecting unit, until it forms a loop along a looped path within which a group of bank notes is fed.
Then, rollers which are part of the projecting unit recover one end of the web previously fed, reducing the size of the loop until the web is brought into contact with the group and binds it with a preset tension.
Following this web positioning operation, a cutting and sealing unit cuts the web and seals the two separate ends of the web, forming a retaining band.
Obviously this operation may be repeated according to the number of bands to be applied to each group of bank notes.
One of the disadvantages of the aforementioned type of machines is that during both the projecting and the push-feed stages, the end of the web, which is out of control and not picked up, is free to assume incorrect positions relative to the circular channel and so may cause jamming or the web may exit the channel.
This disadvantage is most noticeable when the reel is about to finish and its diameter is smaller. During this stage, the profile of the web tends to be more curved than normal and it is more likely that it will assume incorrect positions during the stage in which it is projected towards the infeed of the feed channel.
Moreover, the two separate ends of the web may be incorrectly positioned following the cutting operation. Therefore, for the reasons indicated above, such machines have limited operating speed, are imprecise and are not completely reliable.
The aim of the present invention is to provide a method for banding groups of sheets, in particular bank notes, which can apply bands in a rapid, precise manner and guarantees a strong, high quality end result.
Accordingly, the present invention provides a method for banding groups of sheets in a substantially parallelepiped configuration, the method comprising stages for arranging a group of sheets at a station for the application of at least one retaining band on the group of sheets; using first gripper means to grip the end of a continues web, unwound from a reel and fed in a first direction along a first feed path; drawing the web using the first gripper means, from a starting position adjacent to the banding station, in such a way that it is drawn along a second, closed path, inside which the banding station lies, and returning the end of the web to the starting position, where the end of the web is positioned opposite a section of web extending in an outfeed section of the first feed path; recovering the web using second gripper means, located upstream of the outfeed section of the first feed path, which grip the web and draw it in a second direction which is opposite to the first, so that the web adheres around the group of sheets with a preset tension; sealing the end of the web, at the above-mentioned starting position, to a portion of the section of the web at the outfeed section of the first feed path; cutting the web upstream of the sealing zone relative to the first direction of feed.
The present invention also relates to a machine for banding groups of sheets.
Another aim of the present invention is to provide a machine for banding groups of sheets, which implements the method provided in accordance with the present invention.
Accordingly, the present invention provides a machine for banding groups of sheets in a substantially parallelepiped configuration, the machine comprising a station for applying at least one retaining band to the group of sheets, where pick up and transfer means position a group of sheets; first gripper means which grip the end of a continuous web unwound from a reel and move it in a first direction along a first feed path, the first gripper means being mobile so that they can draw the web from a starting position adjacent to the banding station, along a second, closed feed path inside which the banding station is located, then return the end of the web to the starting position, where it is opposite a section of web extending in an outfeed section of the first feed path; second gripper means, located upstream of the outfeed section of the first feed path, which recover the web, drawing it in a second direction which is opposite to the first, so that the web adheres around the group of sheets with a given tension; sealing means located at the starting position adjacent to the banding station and mobile between a non-operating position and an operating position, in which they seal a portion of the section of web extending along the outfeed section of the first feed path to the end of the web; cutting means for cutting the web upstream of the sealing zone relative to the first direction of web feed.